While advances in early detection and adjuvant therapy for breast cancer have had a favorable impact on patient survival in general, patients who develop advanced metastatic breast cancer are generally likely to face a less favorable prognosis. Commonly used hormonal and chemotherapeutic agents can lead to transient regression of tumors and can also palliate symptoms related to cancer. However, these treatments are often accompanied by toxicities and intolerable side effects and eventually become ineffective in controlling advanced stage breast cancer and its symptoms. Improvements in survival are modest, even with newer targeted biological agents. Moreover, in most metastatic cancers resistance to available conventional treatment ultimately develops or excessive side effects are seen with conventional therapies.
It is interesting to note that greater than 60% of all chemotherapeutic agents used in the treatment of breast cancer are derived from natural substances (Newman 2003). A fairly recent example is the development of taxanes from the Pacific yew tree, Taxus brevifolia. Throughout the world, it is estimated that approximately 80% of the world population still relies on botanical medicine as the primary source of therapy. In the West, botanical medicine is considered a popular form of complementary and alternative medicine among patients diagnosed with cancer. However, few clinical trials have been conducted to firmly assess the safety and efficacy of botanical agents for the treatment of breast cancer, despite anecdotal case reports of cures and clinical efficacy in women who have relied solely on botanical medicine for treatment. It has previously been shown that the aqueous extract of Scutellaria barbata can lead to growth inhibition of breast cancer cell lines in vitro (“Antiproliferative activity of Chinese medicinal herbs on breast cancer cells in vitro,” Anticancer Res., 22(6C):3843-52 (2002)). BZL110, a concentrated aqueous extract of Scutellaria Barbata, was evaluated for antiproliferative activity on five breast cancer cell lines (SK-BR-3, MCF7, MDA-MB-231, BT-474, and MCNeuA). These cell lines represent important prognostic phenotypes of breast cancer expressing a range of estrogen and HER2 receptors. BZL101, tested at a 1:10 dilution (15 μg/ml), demonstrated >50% growth inhibition on four of the five cell lines (Campbell, 2002). BZL101 showed >50% growth inhibition on a panel of lung, prostate and pancreatic cancer cell lines. BZL101 at the same dose did not cause >25% of growth inhibition on normal human mammary cells (HuMEC), demonstrating selectivity to cancer cells (Table 1). More so, BZL101 had a mild mitogenic effect on normal human lymphocytes. In cell cycle analysis, BZL101 caused an S phase burst and G1 arrest. BZL101 also attenuated mitochondrial membrane potential causing caspase-independent high molecular grade (HMG) apoptosis.